MORE DUAL STRING PAIRS FROM ORBIFOLDING

We construct more dual pairs of type II heterotic strings in four dime nsions with N = 2, 1 spacetime supersymmetry. On the type II side the construction utilizes the various possible choices of K3 automorphisms with fixed points which transform the holomorphic two-form nontrivial ly, and rotation plus translation on T-2. The Calabi-Yau orbifolds so obtained have non-zero Euler numbers, so quantum corrections exist on the type IIA strings. The heterotic string (asymmetric) orbifold duals are found which depend on going to the enhanced symmetry points. Some aspects of the construction are discussed including the role of the s ingularity and the possibility of going beyond the adiabatic argument. Many of these examples have also orientifold analogs.